It is oftentimes desirable to determine the psychological state of a subject. For example, it may be desirable to determine if a subject is under stress, fatigued, attempting to deceive or is otherwise experiencing a particular psychological state. For example, it may be desirable to evaluate the veracity of a subject's statements so as to identify instances in which a subject is lying or is otherwise attempting to deceive.
In this regard, an instrument for detecting and measuring physiological changes such as increased pulse rate, muscle tremor, perspiration and subdermal blood flow, that accompany emotional stress, such as the stress created by attempts to deceive, is commonly referred to as a polygraph. A polygraph typically includes multiple sensors that are directly connected to a subject for measuring multiple physiological parameters. Standard polygraph sensors include a blood pressure cuff, a pair of respiration belts, and skin resistance finger electrodes for measuring pulse rate, respiration rate and the galvanic skin response (GSR) of the subject, respectively. All of these physiological parameters are generally coupled to data collection and recordation equipment.
GSR reflects the emotional stress level of the subject by providing a measure of skin conductivity or resistance, which is largely influenced by sweat gland activity. The sweat glands secrete perspiration that flows to the surface of the skin. The perspiration includes liquid and electrolytes; therefore, perspiration facilitates electrolytic conduction at the surface of the skin. GSR testing typically includes attaching electrodes to separate fingers of the same hand and attaching a galvanometer to the electrodes to measure the conductance or resistance between the electrodes.
Having to attach electrodes to a subject to measure their GSR can be disadvantageous in some circumstances. The electrodes are invasive, and therefore they can be uncomfortable to the subject and can themselves cause the individual being tested to become stressed. The invasive and stressful nature of conventional GSR testing can disadvantageously contribute to people's hesitance to be subjected to GSR and polygraph examinations, and to some degree also complicates the interpretation of the results of such examinations. Moreover, a conventional polygraph is not readily portable, is difficult to use, requires a highly trained operator and is not always trustworthy.
Another conventional technique for detecting stress, emotion, fatigue, deception or other similar psychological states of a subject utilizes functional magnetic resonance imaging (MRI). An MRI technique detects metabolic activity in neural tissue and provides corresponding three dimensional images with those regions of the neural tissue exhibiting metabolic activity being indicated or highlighted. The equipment required for an MRI examination, however, is quite expensive and the conduct of an MRI examination may again cause a subject to be uncomfortable and create additional stress for the subject, thereby complicating the interpretation of the images created by the MRI examination.
In addition to generally detecting stress and, more particularly, detecting the stress attributable to efforts by the subject to deceive, it may sometimes also be desirable to detect other psychological states, such as fatigue. For example, it would be desirable to determine if personnel that perform certain critical functions, such as air traffic control or other flight operations functions, were becoming fatigued since the fatigue, in turn, could lead to the degradation of their performance. Likewise, with the elevated concerns regarding terrorism, it would be desirable to reliably evaluate subjects, preferably in a relatively rapid manner, to determine if the subjects are experiencing stress or other emotions that may be indicative of their intent to commit a terrorist act. To date, however, the techniques utilized to detect and measure the physiological changes that accompany stress, such as polygraph and MRI techniques, are not readily scalable and generally require a highly trained and skilled technician to administer and/or interpret the results.
As such, it would be desirable to provide an improved technique for detecting stress, emotion, fatigue, deception or other similar psychological states of a subject. In this regard, it would be desirable to provide a method and apparatus for detecting stress, emotion, fatigue, deception or other similar psychological states of a subject in a manner that is reliable, relatively non-invasive, relatively inexpensive and can be performed in a rapid manner by an operator that need not have extensive training to administer the test and/or interpret the results.